This blog is part of the Agriculture and Ecosystems Blog’s month-long series on Ecosystem Services.

Can you name a highly populated place facing tough natural challenges to ecosystem services? We would say Cairo and Lima, two of the largest cities in the world located in a desert. What better places to focus on in a water research institute?

Parque Huascar, Lima. Photo: Caretas

In Lima, with only 13 mm of rain over the year (about half of what Cairo gets), every drop counts. And so does the reuse of water, be it from rain, wells or the Rimac River, which passes the city. There are many reuse activities, formal and informal; while untreated wastewater is, for example, used informally for vegetable farming at scale, formal reuse of treated wastewater remains limited by law to parks and gardens (a common paradox).

Treated wastewater creates a recreational oasis

However, in a city of dust and sand, these parks can change lives. Take Park Huascar, for example; a multi-purpose park with a big lake offering educational parcours, a small zoo, recreational areas, a tree nursery, demonstration farms, playgrounds, a soccer field, and picnic areas under shady trees. A beautiful green island in a dry urban landscape, and an oasis with replication value the city is proud of.

The park receives its water from one of Lima’s 15 wastewater treatment plants. The treated wastewater is free because the treatment plant and the park are on public grounds. In a landscape where most kids grow up without trees, the social benefit of wastewater reuse for creating green space appears immense.

Win-win

The Huascar case of combining wastewater treatment and a public park is in fact a classic win-win situation of reuse: it reduces pollution and optimizes resource recovery and consumption in an urban area. This has important benefits for ecosystems and the services they provide to people (see diagram below).

The treated wastewater supplies important resources to the park such as water and nutrients, which are extremely valuable where soils are ‘dry’ and ‘unfertile’ such as in Lima. As a consequence, the park does not need to irrigated water from the tap, saving freshwater for other uses and replacing important elements/nutrients into soils. With treated wastewater, plants and flowers can grow in the park, creating a recreational ‘oasis’ in the middle of the Peruvian capital, one of the cities with least green space per capita in the world.

Two important local ecosystem services (ESS) are directly enhanced through wastewater use:

Recreational, mental and physical health of citizens, as the park green area provides an important space for physical and mental relaxation and recreation for both adults and children;

Erosion prevention and maintenance of soil quality, as the nutrients and the organic matter in the wastewater enhance soil structure, fertility and microbiological activity. This is an important contribution to long-term soil sustainability, particularly in areas prone to land degradation.

Wastewater irrigation in the park also promotes carbon sinking over the mid-to-long term, given the increase in soil organic matter and vegetation. This means that carbon is sequestered in soils and trees, offsetting of greenhouse gas emissions and enhancing the carbon sequestration and the local and global climate regulation ESS.

Impact on ESS and human well-being of wastewater irrigation in Huascar Park, Lima.

Risks such as heavy metals and salts accumulation in soils are not known, largely as the treatment plant only serves residential (and not industrial) districts, and cases of pathogen contamination are not reported. This indicates that the wastewater and its reuse are safe.

Hence, wastewater irrigation in Huascar does not cause any negative trade-offs. Instead, it creates synergies amongst different ESS, highlighting the fact that resource recovery and reuse (RRR), when properly designed and managed, is a win-win solution for urban citizens, urban ecosystems, and wastewater management. Wastewater irrigation can also be scaled up.

Reuse and sustainable intensification

In his initial blog post, CGIAR Research Program on Water, Land and Ecosystems (WLE) Director Andrew Noble suggested three thematic areas for the program:

Sound and efficient resource use,

Restoring land productivity, and

Reducing risk and uncertainty.

Without question, avoiding resource loss by recovering and reusing water and nutrients will contribute to efficient resource use, help restore land productivity and increase the resilience of systems against risks, like spiking fertilizer prices. Resource recovery and reuse (RRR), one of four research areas of WLE, supports ecosystem services beyond agricultural production.

The ecosystem services provided by wastewater reuse, if well managed, represents an important opportunity for costs savings. The social benefits that the park creates probably offsets its operational costs by far.

Some of the key research questions we are trying to address in RRR:

Can a set of key indicators or proxies be identified to quantify and better manage the various linkages/ dependencies between RRR and ESS?

How to value the social benefits of ESS? For example, compared to wastewater treatment costs and park maintenance, what is the best way to assess the overall costs and benefits of welfare-oriented RRR business models?

Lima is one of nine focus cities that the CGIAR Research Program on Water, Land and Ecosystems (WLE) strategic research portfolio on Resource Recovery and Reuse (RRR) is targeting for testing the feasibility of reuse business models. The Huascar Park is only an example among several that the larger Lima region offers.

Luca di Mario is part of the Resource Recovery and Reuse Team with the CGIAR Research Program on Water, Land and Ecosystems (WLE). Pay Drechsel leads the Strategic Research Program on Resource Recovery and Reuse within WLE and is theme leader of Water Quality, Health and Environment at the International Water Management Institute.

Related contents

Much of the developing world, including Sri Lanka, is facing an organic waste challenge, but the right economic incentives and business models can help turn waste into food and energy, WLE/IWMI told a recent business forum in Colombo.

WLE researchers based at ICRAF have authored a chapter in the recently launched GII 2018 report, highlighting the making of fuel briquettes from organic residue as an important innovation for Sub-Saharan Africa.

Related publications

Rankin, Sara; Bonilla-Findji, Osana. 2019. What can the Latin American cities of Cali, Quito and Medellín learn from each other’s efforts to build sustainable food systems?. Colombo: Sri Lanka. CGIAR Research Program on Water, Land and Ecosystems.9p.

Kallio, M. 2018. The impacts of Hydropower and Mining on Water Quality: an example from the Nam Ngum Catchment, Lao PDR. Water Knowledge #2. Vientiane, Lao PDR, CGIAR Research Program on Water, Land and Ecosystems.

Amerasinghe, Priyanie; Dey, Dipayan. 2018. Recommendations for the wise use of urban and peri-urban wetlands in Kolkata, India. Colombo, Sri Lanka: International Water Management Institute (IWMI). CGIAR Research Program on Water, Land and Ecosystems (WLE). 8p. (WLE BRIEFING SERIES NO. 23 )

Big Question

We are celebrating the launch of WLE's Ecosystem Services and Resilience Framework with a month long focus on ecosystem services, provided from natural and human-modified ecosystems, starting with the blog posts surrounding the Ecosystem Services Partnership conference.

Next response

The role of agriculture in human wellbeing goes beyond crop production. Bali’s traditional rice terrace farming, the subak system, provides a good illustration of the bundle of ecosystem services provided by agricultural landscapes.

Comments

Max Joneson April 20, 2017

I think the idea of wastewater services are so cool. I love that you talked about a park in your article that receives free water from wastewater service plants. I think that is a great way to fund city parks is through recycling the wastewater, and saving more good water for use! Thanks for sharing this great information! http://www.nrclabs.com/public-water-systems/

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